Overview

A board member of Huntsville's Downtown 47 and a member of their investment committee approached us on May 28th, 2013 with an interesting proposition. They are "interested in a project to build a wall covered with LED lights that illuminate when the diodes come in contact with water. Our intent is to place the wall in Big Spring Park as a 'water graffiti' exhibit". A similar project was undertaken by Antonin Fourneau in Poitiers, France (video).

Requirements

The group is willing to spend a decent amount of money to get this built, they don't want to cheap out on the project. They are willing to provide the money for a quality production.

Our contact thought that 6' by 18' is a good size for the wall, but it is open for negotiation.

Timeline is flexible; they would prefer that it would be done before it starts getting cold again, but if it takes until next summer, that may be acceptable.

The exhibit will be transportable, and would not need to be left outside 24/7. It will be pulled out and set up for events as necessary.

We would likely be able to keep the wall at the shop (only if we want!) to show off when the city isn't using it. (I know there are mixed feelings about this; they will not try to force us to hold it if we don't want to)

They are very excited about Makers Local and the hackerspace scene, and would love to include us in things like this in the future.

They are willing to pay for a small demo board to show off how the wall would work, and give us a chance to determine a more accurate budget/timeline before ordering thousands of LEDs.

Depending on the cost, they are interested in looking into extra features/improvements of the LED wall.

It needs to be safe (obviously); I don't think this will be an issue, if we take the proper precautions.

Power Supply

Frame

Cost Estimation

PCB Manufacture

PCB Option 1

I also got a quote for a limited run of just 5 boards: $684 + shipping (~$137 per board)

LEDs

Frame

Power Supply

Prototypes

Version v0.1 - complete

This 5"x3" 6-LED prototype was made completely in-house. The single-sided PCB was created using an etch-resist mask cut by the vinyl cutter, and the holes were drilled with the drill press. Six blue LEDs and two 3V coin-cell batteries were used to populate the board.

Verdict: Pad shape did not seem to make a difference on water conductivity. Basic circuit idea works very well.

Cost: $0 (used materials that were on-hand)

Version v0.2 - awaiting PCB arrival

This prototype will consist of 10 6"x6" double-sided PCBs with black soldermask and solder-tinned pads. This prototype will give a better feel for the finished product, and can be used as a sample/demonstration to show off to others. Features that we'd like to see in this prototype are inter-connectivity*, water resistance, and overall aesthetics. This prototype will also help provide a better estimate for the time required to assemble the boards by hand. I'm going to try to work in some sort of music controller as well, using parts I have on-hand.

Volunteering

This is a rather large undertaking, so we'll need as many people participating as we can get! If you're interested in helping out with any of the tasks below, feel free to add yourself. If you want to help, but don't know what to do, add yourself to the "Helper" section. More than one person can be in each section, and one person can be in more than one section.

PCB Design

The wall will consist of many interconnected LED PCB boards that contain built-in water sensors. This team will handle designing and manufacturing these PCB boards.

Power Supply System

The wall will require a moderately hefty power supply system to power all of the LEDs and a way to get this power to the boards. We also need to ensure that the system is safe, since we're dealing with water and electricity. This team will need to choose a power supply (or multiple supplies), and determine the best way to route power safely from the supply to the LED boards.

Wall Structure Design/Assembly

Building the physical wall using the PCBs is non-trivial and will need some careful design and thought. This team will help decide on materials and structural components, and will help build the wall's physical supports.

Auxiliary Output

Some "bonus" ideas have been floating around to give the wall more unique and amazing features. The idea of adding some sort of sound output from the wall is the proposed feature with the most attention at the moment. This team will design hardware and software that will receive input from the wall and produce some sort of auxiliary output on a laptop, mobile device, speakers, etc.

PCB Soldering/Assembly

Once the PCBs are made and shipped, they will need to be assembled. The wall may exhibit over 15,000 LEDs so as many hands as possible will be needed to solder them all onto the boards. This team will assemble the final PCBs by soldering LEDs to each board and test the completed boards.

Photography and Documentation

One of the main goals of the project is to show off what Makers Local 256 is capable of doing. We'll need photos, videos, write-ups, and general documentation of the process to record our progress an successes. This team will be in charge of taking photos and videos of soldering events, wall construction, prototype assembly, circuit testing, and pretty much any other aspect of the project.

Helpers

If you don't know what to do, add yourself here, and we can help you find something!

Progress Log

00:56, 11 June 2013 (CDT): Started the wiki page with some PCB cost information. We have also created a small sample prototype to prove the viability of the overall idea. The prototype worked very well, and it seems that the water-sensor shape does not really have much effect on the LED brightness or conductivity of the water.

13:58, 19 June 2013 (CDT): We demonstrated the board and got some great feedback and ideas. We were given the go-ahead to draw up a design for more "finished" prototype in order to give a better feel for the final product and the time it will require to build it. One possibly feasible idea that merits investigation is using the same water pads to control a MIDI (or similar) instrument when water hits the pads.

12:44, 15 July 2013 (CDT): Prototype v0.2 PCB design has been completed and sent off to the fab house, and we're awaiting its completion. All of the parts for this prototype have arrived, except the PCB, so assembly of the prototype will begin when the boards arrive.